Endarti, Dwi, and Arthorn Riewpaiboon. “VACCINATION EXTERNALITIES: THE CONCEPT AND APPLICATION IN PHARMACOECONOMIC STUDIES”. Asian Journal of Pharmaceutical and Clinical Research, vol. 9, no. 1, Jan. 2016, pp. 204-8, https://www.journals.innovareacademics.in/index.php/ajpcr/article/view/9564.